Hazardous waste material is a waste material that has properties that make it dangerous or potentially harmful to human health or the environment. The universe of hazardous waste is large and diverse. Hazardous waste includes chemical waste, biological waste, radioactive waste, and the like. Hazardous waste can be found as a liquid, solid, contained gas, sludge, slurry, and the like. Hazardous waste is often a by-product of manufacturing processes or simply discarded commercial products, like cleaning fluids or pesticides.
There are a host of hazardous wastes that are difficult to dispose of due to the possibility of contamination of the environment and/or those that handle the hazardous waste during disposal. These hazardous wastes include materials such as dioxins, polychlorobiphenyls, heavy metals, sewage, radioactive materials, and the like.
Radioactive waste is one example of a hazardous waste material that is subject to strict regulations governing disposal and handling of the waste. In the United States, radioactive waste may be classified in one of the following general categories: (1) spent nuclear fuel from nuclear reactors and high-level waste from reprocessing spent nuclear fuel, (2) transuranic waste resulting mainly from by-products of defense programs, (3) uranium mill tailings resulting from mining and milling of uranium ore, (4) low-level waste resulting from contaminated industrial or research waste, and (5) naturally occurring radioactive materials. Mixed waste is waste that may contain both radioactive components and other hazardous components. Other countries may use similar or different terms to classify radioactive waste that is treated in a similar manner (e.g., Intermediate Level Waste (ILW) in the U.K. is treated in roughly the same way as transuranic waste is treated in the U.S.).
Transuranic, or TRU, waste generally includes materials such as soils, sludges, solids, and the like that have been contaminated with manmade radioisotopes heavier than uranium. These elements may include plutonium, neptunium, americium, curium, and californium. Transuranic waste can be produced as a result of reprocessing spent nuclear fuel, during nuclear fuel assembly, and during nuclear weapons research, production, and cleanup.
Transuranic waste may be divided into the following categories, based on its level of radioactivity: contact-handled transuranic waste (CH-TRU) and remote-handled transuranic waste (RH-TRU). CH-TRU is typically packaged in 55-gallon metal drums that can be handled under controlled conditions without any shielding beyond the container itself. The maximum radiation dose at the surface of a contact-handled transuranic waste container is approximately 200 millirems per hour. Contact-handled waste primarily emits alpha particles that may be shielded by a sheet of paper or the outer layer of a person's skin.
RH-TRU emits more radiation than contact-handled transuranic waste and therefore is typically handled and transported in shielded containers. Surface radiation levels of unshielded containers of remote-handled transuranic waste exceed 200 millirems per hour. Remote-handled waste primarily emits gamma radiation, which may be highly penetrating and requires concrete, lead, or steel to block it.
Conventionally, one way to dispose of hazardous waste has been to encapsulate the hazardous waste in cementitious material. Typically, this is done by mixing the cementitious material and the hazardous waste together in a suitable container, e.g., a 55-gallon drum. The cementitious material solidifies to form a solid block of encapsulated waste inside the container.
Unfortunately, conventional systems and techniques for filling the container suffer from a number of drawbacks. In conventional systems, the container is supplied with dry cementitious powders at the same time, or just before or just after, the container is filled with hazardous waste. This causes cement dust to build up on the equipment used to handle the hazardous waste resulting in increased maintenance requirements. The HEPA filters are especially impacted because they must prevent the cement dust from leaving the confined filling area (e.g., a glove box). The cement dust may be considered to be contaminated for purposes of handling and disposal since the cement dust is in the same area as the hazardous waste.
Another problematic aspect of conventional systems is that the container may be moved from station to station with the container open thereby increasing the potential for contamination. For example, a conventional system may move the container between stations to perform the following actions: take the lid off the container, fill the container with hazardous waste, add cement, and put the lid back on the container. Moving the open container multiple times in this manner only serves to increase the potential for the spread of contamination to the exterior of the container, the processing equipment, and/or the worker.